This invention relates to liquid sampling devices and more particularly to blood collection devices used to obtain blood samples for blood-gas analysis.
Blood-gas analysis machines are used in measuring the amounts of gases, such as oxygen and carbon dioxide, in a patient's blood. Blood obtained from a patient will absorb or release oxygen when exposed to an atmosphere having a gas or oxygen content different from that of the blood. For example, the oxygen content of arterial blood is often measured in patients suffering from heart and lung diseases. In order to obtain reliable or accurate test results, it is important to prevent or miminize the exposure of the blood sample to contaminating gas atmospheres during the taking of the sample, storage and transportation to the gas analyzing machine. In U.S. Pat. No. 3,867,923, collection devices are disclosed which have a bag that is normally maintained collapsed until the blood enters and expands the bag. With the collection devices of the above patent, however, the air originally in the needle cannula and internal passageways of the devices remains with the sample of blood, and oxygen in such air can be absorbed by the blood. While air could be expelled from the bag after it is filled by compressing the bag with the needle pointing upwardly, such removal of air would tend to result in the undesirable issuance of some blood from the needle. Also, since the air is in contact with the blood during the time it takes to fill the bag, some absorption of oxygen occurs.